A foveal optical system is an optical system that mimics the function of the human eye, and is an optical system with an extremely wide field of view, and that affords high resolution if we focus on the center part of the field. Optical systems such as this have been described, for example, in Japanese Laid-Open Patent Applications 2004-354572 and 2000-221391.
[Patent Document 1] Japanese Laid-Open Patent Application 2004-354572
[Patent Document 2] Japanese Laid-Open Patent Application 2000-221391
[Patent Document 3] Japanese Laid-Open Patent Application 2003-167195